Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 060326 AAA
AFDFSD

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Sioux Falls SD
1026 PM CDT Wed May 5 2021

.SHORT TERM...(This Evening through Thursday)
Issued at 231 PM CDT Wed May 5 2021

Area of WAA driven showers continues to move eastward through NW
IA/SW MN this afternoon and should exit the area by evening.
Meanwhile, a surface low currently analyzed along the MO River in SE
SD/NE Neb has provided enough forcing for an arcing line of weak
thunderstorms through NE Neb which may drift toward our far SE SD
counties and eventually Hwy 20 in NW IA. Mid afternoon RAP
mesoanalysis suggest roughly 200-500 J/kg of SBCAPE in this area and
while quite unlikely, with a bit of enhanced near surface vorticity,
the main concern would be the (small) potential for a brief
funnel/landspout with any convection. Meanwhile further west, a
second cluster of weak convection in south central SD may
occasionally produce gusts to around 50 mph with a dry subcloud
layer noted in the soundings.

Surface high pressure drifts down to through central SD overnight
and will set up the potential for frost producing temperatures. A
few question marks remain however in regards to cloud cover with a
few model solutions hanging on to either a mid level deck or worse
yet, a low stratus deck. Areas south of I-90 seem to be favored for
this cloud contamination but SREF probabilities for reduced ceilings
are not overly impressive. For this reason, have kept overnight lows
roughly near the 50th percentile which still produces widespread
lower to mid 30s over about the northwest 2/3rds of our forecast
area. With dewpoint depressions supportive of frost, have issued a
Frost Advisory for this area as well.

Quiet conditions return for Thursday with added sunshine and
afternoon temperatures in the 60s. While the better SPG remains to
our east, still could see some gusts in the 20-25 mph range. Of more
important note is various forecast soundings showing 25-30 mph of
wind at the top of the mixed layer along the Buffalo Ridge, which
combined with RH values in the lower to mid 20s, could result in
enhanced fire weather concerns. After collaboration with our fire
weather partners, have held off on any headlines given the recent
rainfall and greenup.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 231 PM CDT Wed May 5 2021

Ridge axis shifts east for Friday with continued quiet conditions
across our immediate area. Again, temperatures in the 60s look to be
a good bet although perhaps a bit cooler across SW MN where a weak
backdoor cold front and north/northeasterly winds may keep
temperatures in the upper 50s.

Attention for Saturday turns to cut off low dropping through the Pac
NW. The main baroclinic zone as well as instability axis looks to
remain to the southwest of our forecast area and thus the better
convectively enhanced rainfall amounts should remain void of our
area as well. There is still a fairly good zone of broad synoptic
lift further east however and thus lighter showers could still very
well be in the mix for at least the western half our area. Last few
deterministic runs of the global models have shown a southwestward
shift with the QPF axis which is supported by the ECMWF ensemble as
well. In either case, outside of maybe the GFS, does not look like
any rainfall amounts would make a significant impact to our ongoing
drought.

For Sunday into early next week, previously mentioned cutoff low
wobbles across the intermountain west while a second cut off sinks
toward the Great Lakes region. This leaves our region in an area of
muddled shortwave ridging. Temperatures will likely remain on the
cool side of normal with mid 50s to mid 60s fairly common.
Precipitation chances also look to remain minimal.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1021 PM CDT Wed May 5 2021

MVFR ceilings will continue to shift eastward but may still impact
areas along and east of a FSD to SUX line before 12z. Otherwise
VFR conditions should prevail through the forecast period. Expect
north winds to gradually weaken overnight as sfc high pressure
builds in. Winds will increase with mixing Thursday morning.
During the afternoon, expect gusts up to 25 kts and diurnally
driven mid level cumulus.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory from 3 AM to 8 AM CDT Thursday for SDZ038>040-050-
     052>069.

MN...Frost Advisory from 3 AM to 8 AM CDT Thursday for MNZ071-072-080-
     081-089-097-098.

IA...Frost Advisory from 3 AM to 8 AM CDT Thursday for IAZ001.

NE...NONE.
&&

$$

SHORT TERM...Kalin
LONG TERM...Kalin
AVIATION...BP


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